To rigorously examine physiologic alterations that occur during SIV infection we have begun examining intestinal segments in ssing chambers. ssing chambers are the "gold standard" for characterizing the physiology of the intestine in a rigorous, quantitative fashion. In preliminary studies we have examined duodenum, jejunum and ileum in duplicate from five normal, uninfected macaques and seven SIV-infected macaques. We found that duodenal, jejunal and ileal tissues can be harvested from macaques mounted in ssing chambers, and subsequently display extremely consistent, site-specific, transepithelial resistances indicative of healthy, physiologically active intestinal epithelium. Furthermore, duodenal, jejunal and ileal tissues display consistent site-specific responses to the secretagogue theophylline, and to glucose which stimulates absorption. Animals infected with SIV had marked changes in these